Many patients with Hodgkin's disease have immune responsiveness primarily manifested by deficient cell-mediated immunity and increased susceptibility to opportunistic infection. A subpopulation of T-lymphocytes has recently been shown to suppress the function of B and T lymphocytes, leading to impaired humoral immunity and allograft rejection. Suppressor cells have also been implicated in decreasing marrow cell proliferation and differentiation in congenital and acquired hypoplastic anemias. The primary objective of this study is to delineate and characterize suppressor T-cell activity in patients with Hodgkin's disease and non-Hodgkin's lymphoma. The presence of histamine receptors on surface of lymphocytes has allowed for the preferential removal of the suppressor cell population by passing purified lymphocyte preparations through columns of histamine-coated Sephadex beads. Following passage through the column, the non-retained lymphocytes demonstrate a marked increase in the previously suppressed cytotoxicity responses to allogenic lymphocytes. Methods for elution and identification of the retained lymphocyte population will be investigated so that the function of these cells may be evaluated and compared to other lymphocyte fractions. Lymphocyte-lymphocyte interaction will be tested by the mixed leukocyte (MLC) and the cell mediated lympholysis (CML) assays. The suppressive action on non-lymphocyte cells will be evaluated by the erythroid and granulocytic colony forming assays. Further investigations will evaluate the interaction of soluble factors in serum and MLC supernatants with the suppressor and effector lymphocyte populations. A better understanding of the mechanisms leading to suppression of cellular immunity in patients with Hodgkin's disease and non-Hodgkin's lymphomas will help to identify patients with increased risk of developing opportunistic infections and aid in designing optimum treatment programs.